cmd/stcrashreceiver, lib/db: Improve panic message handling (#7029)

lib/db/lowlevel.go

@@ -13,6 +13,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"regexp"
 	"time"
 
 	"github.com/dchest/siphash"
@@ -816,7 +817,7 @@ func (db *Lowlevel) getMetaAndCheck(folder string) *metadataTracker {
 	var err error
 	defer func() {
 		if err != nil && !backend.IsClosed(err) {
-			panic(err)
+			warnAndPanic(err)
 		}
 	}()
 
@@ -944,14 +945,14 @@ func (db *Lowlevel) verifyLocalSequence(curSeq int64, folder string) bool {
 
 	t, err := db.newReadOnlyTransaction()
 	if err != nil {
-		panic(err)
+		warnAndPanic(err)
 	}
 	ok := true
 	if err := t.withHaveSequence([]byte(folder), curSeq+1, func(fi protocol.FileIntf) bool {
 		ok = false // we got something, which we should not have
 		return false
 	}); err != nil && !backend.IsClosed(err) {
-		panic(err)
+		warnAndPanic(err)
 	}
 	t.close()
 
@@ -1161,3 +1162,11 @@ func (db *Lowlevel) needsRepairPath() string {
 func unchanged(nf, ef protocol.FileIntf) bool {
 	return ef.FileVersion().Equal(nf.FileVersion()) && ef.IsInvalid() == nf.IsInvalid() && ef.FileLocalFlags() == nf.FileLocalFlags()
 }
+
+var ldbPathRe = regexp.MustCompile(`(open|write|read) .+[\\/].+[\\/]index[^\\/]+[\\/][^\\/]+: `)
+
+func warnAndPanic(err error) {
+	l.Warnf("Fatal error: %v", err)
+	msg := ldbPathRe.ReplaceAllString(err.Error(), "$1 x: ")
+	panic(msg)
+}

lib/db/set.go

@@ -531,6 +531,5 @@ func fatalError(err error, opStr string, db *Lowlevel) {
 			}
 		}
 	}
-	l.Warnf("Fatal error: %v: %v", opStr, err)
-	panic(err)
+	warnAndPanic(fmt.Errorf("%v: %w:", opStr, err))
 }